With the improvement of user terminals such as smartphones and development of mobile communication technology, a user can use various types of contents such as pictures, videos, audios, applications, and the like by accessing a web server provided by a content provider (CP) through a user terminal anytime anywhere. Furthermore, the frequency of using contents through mobile networks (e.g. a mobile communication network) which ensure mobility of users continuously increases.
However, since the number of users who want to access web servers rapidly increases although the number of web servers provided by content providers is limited, many problems including data loss, bottleneck phenomenon, transmission delay, instability such as non-continuous data transmission, etc.
In order to solve these problems, a Content Delivery Network (CDN) is provided.
The CDN is a service for stably transmitting various types of contents such as pictures, movies, music videos, and the like to a user terminal. Specifically, in the CDN service, some or all contents stored in a web server of a content provider located at a distance from a user terminal, e.g., contents having large capacity such as images, videos, and audios, or contents frequently requested by a user terminal, are previously copied and stored in cache devices widely distributed at main points in a network. Upon reception of a content request message from the user terminal, the closest cache device to the user terminal transmits the content to the user terminal in response to the content request message. This may improve a content access speed and stably provide contents.
The CDN service having the above-described advantages is introduced for wired networks first. Although some technologies for applying the CDN service to mobile networks are proposed, a method of effectively detecting a handover of a user terminal which occurs during content transmission in a wireless CDN network has not been provided yet.
For example, in LTE (Long Term Evolution), there are various cases regarded as a handover caused by the movement of user terminal, including a case in which only an eNodeB is changed, a case in which both an eNodeB and an MME (Mobility Management Entity) are changed, a case in which both an eNodeB and an S-GW (Serving Gateway) are changed, a case in which all of an eNodeB, an MME and an S-GW are changed, and a case of transfer from LTE network to 3G network and vice versa (i.e., a vertical handover). For this, however, a cache device should be designed in consideration of the structure and characteristics of each network.
Detecting a handover of a user terminal during content transmission in a mobile network without recognition of the structure and characteristics of the network is a design consideration of the inventor(s).